Switching voltage regulators generate an output voltage from an input voltage and are implemented with active components such as a pulse width modulation controller (PWM), driver, power MOSFETs, and passive components such as inductors, transformers or coupled inductors, capacitors, and resistors. Controllers typically measure the output current and output voltage in order to regulate and monitor the output voltage. Measuring the input current and input voltage allow the controller to improve regulation and monitoring, as well as monitoring input power for voltage, current, and power constraints.
Knowledge of the regulator input current and voltage is required in some controllers for improved regulation algorithms and monitoring input power for voltage, current, and power constraints. Measuring the input current and voltage requires external and internal circuitry in the controller. Input voltage is an existing measurement for many conventional voltage regulators. Then, only input current must be known to obtain the input power of the power converter.
The input current can be either sensed or estimated. In the case of sensing, input voltage can be sensed directly by scaling down the voltage via a voltage divider. Input current can be sensed using an external amplifier. However, such an approach requires both a high-side shunt resistor and an amplifier. A lower complexity input current and voltage monitor is therefore desirable to minimize regulator complexity and cost.